The invention relates to apparatus for controlling lubricating devices which are actuated by pulses of compressed air, and particularly to apparatus of the type which includes a drive piston which is moved back and forth, in synchronism with the actuation of the devices to be lubricated, by the compressed air provided for these devices, whereby the drive piston actuates a control valve for the introduction of pulses of compressed air to the lubricating devices.
It is known to lubricate machine parts and pneumatically actuated devices by means of a lubricating device which is driven by pulses of compressed air which drives the lubricating device in synchronism with the devices to be lubricated. With such a lubricating device, which includes, for example, an oil pump with series-connected metering elements, or is a directly pnuematically actuated oil gun, a certain minimum quantity discharge takes place with every actuation pulse. In various cases, for example when lubricating small pneumatic cylinders or devices operating at a high operating frequency, too much lubricant is discharged.
It is known to overcome such a drawback by connecting a monitoring device ahead of the lubricating device, the monitoring device causing an actuation or operating signal to be transmitted to the associated lubricating device only after the occurrence of a certain number of switch-on periods of the device to be lubricated.
In a known monitoring device of this type, one example of which is disclosed in German Pat. No. 1,775,703, a drive piston is provided which is moved back and forth by the switch-on pulses of the device to be lubricated and the drive piston is provided with a piston rod which engages, through the intermediary of a transverse pin, in an oblique slit in a sleeve in a manner to cause the sleeve to execute a stepwise rotation with each stroke of the piston. This stepping mechanism drives cams which actuate control valves to control the actuation signals for the lubricating device. This known monitoring device is relatively expensive. Moreover, the setting and varying of the number of switch-on periods which are to take place until a lubricating signal is actuated are complicated and can be effected only within limits.